where history will be made when the justices hear arguments this morning on whether gay marriage is a right guaranteed by the constitution. Spectators have been lining up outside the court for days and our court expert "nightline" anchor terry moran is there. Good morning. Reporter: It's a lot nicer out here for the hundreds waiting in line for days for a seat inside and this is the day. The day that so many millions of americans have waited and struggled for. Others have looked toward with concern and anxiety because in just a few hours, in that court, the six men and three women of the supreme court will take up the huge issue, what is the meaning of marriage in america today and does it include our fellow citizens who are gay? Outside the supreme court overnight a candlelight vigil for proponents of same-sex marriage. A debate that toughs countless american families and in the line outside the court for one of the 60 or so seats inside, a line that began last thursday, that great debate continues. Yeah, I would hope to get married because I'm a gay man and I'm from california, so i would like to get married in my home state. I'm a huge supporter of marriage. I'm a christian and I hold the traditional biblical values. All: No more 8. Reporter: Proposition 8 passed in 2008 defining marriage in that state as only and forever the union of one man, one woman. Paul and his partner jeff decided to take the state to court. Anyone who has fallen in love knows you don't choose who you fall in love with. You just fall in love. There is no choice in the matter. It just happens. Reporter: Chris perry and sandy steer will also be in court today fighting to overturn california's ban on gay marriage. Right now sandy and I are really treated like second class citizens in this state. We're expected to contribute and pay taxes, parent, live up to all the other expectations of everybody else but we're missing this one key fundamental right which is just to be married. Reporter: You know what, this issue is changing in the american mind so fast and the reason is that so many millions of gay people have stood up and told their stories to their families. The families in here too, chief justice john roberts has a cousin who has come out this week to say, I love my cousin, i hope he'll do the right thing. So the kinds of debates that are happening in families and workplaces around the country happen up there too. And she got the ticket from the chief justice. Thanks very much.

This transcript has been automatically generated and may not be 100% accurate.